The 3GPP (3rd Generation Partnership Project) is a project for studying and preparing specifications of mobile communication systems based on networks evolved from W-CDMA (Wideband-Code Division Multiple Access) and GSM (Global System for Mobile Communications). The 3GPP standardized W-CDMA systems as the 3G cellular mobile communication system, and the services have been started sequentially. Further, the 3GPP has standardized HSDAP (High-Speed Downlink Packet Access) with communication rates further increased, and the services have been started. In the 3GPP, using evolution (hereinafter, referred to as “LTE (Long Term Evolution)” or “EUTRA (Evolved Universal Terrestrial Radio Access)”) of the 3G radio access techniques and wider frequency bands, studies have proceeded on mobile communication systems (hereinafter, referred to as “LTE-A (Long Term Evolution-Advanced)” or “Advanced-EUTRA”) for actualizing transmission and reception of data of higher rates.
As the communication schemes in LTE, considered are an OFDMA (Orthogonal Frequency Division Multiple Access) method for performing user multiplexing using mutually orthogonal subcarriers, and an SC-FDMA (Single Carrier-Frequency Division Multiple Access) method. In other words, the OFDMA method that is a multicarrier communication scheme is proposed in downlink, and the SC-FDMA method that is a single-carrier communication scheme is proposed in uplink.
Meanwhile, as the communication method in LTE-A, the OFDMA method is considered in downlink, and in uplink, in addition to the SC-FDMA method, considered is Clustered-SC-FDMA (Clustered-Single Carrier-Frequency Division Multiple Access, also referred to as DFT-s-OFDM with Spectrum Division Control and DFT-precoded OFDM). Herein, the SC-FDMA method and Clustered-SC-FDMA method, which are proposed as the uplink communication scheme in LTE and LTE-A, have characteristics that it is possible to control the PAPR (Peak to Average Power Ratio, transmit power) in transmitting data (information) to within low levels, due to performance (single-carrier performance) of single-carrier communication method.
Further, in LTE-A, in contrast to general mobile communication systems in which used frequency bands are contiguous, it is considered to use a plurality of contiguous and/or non-contiguous frequency bands (hereinafter, referred to as “component carriers (CCs)” or “carrier components (CCs)”) in a composite manner to operate as a single frequency band (a wider frequency band) (also referred to as carrier aggregation, spectrum aggregation, frequency aggregation and the like). Further, in order for the base station apparatus and the mobile station apparatus to communicate using the wider frequency band more flexibly, it is also proposed to set different frequency bandwidths on a frequency band used in communications in downlink and a frequency band used in communications in uplink (Asymmetric carrier aggregation) (Non-patent Document 1).
FIG. 10 is a diagram to explain a mobile communication system subjected to carrier aggregation in conventional techniques. Setting the same bandwidth on a frequency band used in communications in downlink (DL) and a frequency band used in communications in uplink (UL) as shown in FIG. 10 is also referred to as Symmetric carrier aggregation. As shown in FIG. 10, the base station apparatus and the mobile station apparatus use a plurality of component carriers that are contiguous and/or non-contiguous frequency bands in a composite manner, and are capable of performing communications in the wider frequency band comprised of a plurality of component carriers. As an example, FIG. 10 shows that the frequency band (hereinafter, referred to as a DL system band and DL system bandwidth) with a bandwidth of 100 MHz used in communications in downlink is comprised of five downlink component carriers (DCC1: Downlink Component Carrier 1, DCC2, DCC3, DCC4, and DCC5) each with a frequency bandwidth of 20 MHz. Further, as an example, FIG. 10 shows that the frequency band (hereinafter, referred to as a UL system band and UL system bandwidth) with a bandwidth of 100 MHz used in communications in uplink is comprised of five uplink component carriers (UCC1: Uplink Component Carrier 1, UCC2, UCC3, UCC4, and UCC5) each with a frequency bandwidth of 20 MHz.
In FIG. 10, downlink channels such as Physical Downlink Control Channel (PDCCH), Physical Downlink Shared Channel (PDSCH) and the like are mapped on each downlink component carrier. The base station apparatus allocates control information (resource allocation information, MCS (Modulation and Coding Scheme) information, HARQ (Hybrid Automatic Repeat Request) processing information) and the like) to transmit a downlink transport block to be transmitted using the PDSCH to a mobile station apparatus using the PDCCH, and transmits the downlink transport block to the mobile station apparatus using the PDSCH. In other words, in FIG. 10, the base station apparatus is capable of transmitting up to five downlink transport blocks to the mobile station apparatus in the same subframe.
Meanwhile, uplink channels such as Physical Uplink Control Channel (PUCCH), Physical Uplink Shared Channel (PUSCH) and the like are mapped on each uplink component carrier. The mobile station apparatus transmits uplink control information (UCI) including control information of HARQ (Hereafter described as HARQ control information), channel state information, scheduling request and the like to the base station apparatus using the PUCCH and/or the PUSCH. Herein, the HARQ control information includes information indicative of ACK/NACK (a Positive Acknowledgement/a Negative Acknowledgement, ACK or NACK) for the PDCCH and/or a downlink transport block and/or information indicative of DTX (Discontinuous Transmission). The information indicative of DTX is information indicating that the mobile station apparatus was not able to detect the PDCCH transmitted from the base station apparatus (or may be information indicating whether the mobile station apparatus was able to detect the PDCCH).
Herein, in FIG. 10, a downlink/uplink component carrier may exist on which any downlink/uplink channel such as the PDCCH, PDSCH, PUCCH and PUSCH is not mapped.
Similarly, FIG. 11 is a diagram to explain a mobile communication system subjected to asymmetric carrier aggregation in the conventional techniques. As shown in FIG. 11, different bandwidths are set on a frequency band used in communications in downlink and a frequency band used in communications in uplink, and the base station apparatus and the mobile station apparatus use component carriers that are contiguous and/or non-contiguous frequency bands constituting the frequency bands in a composite manner, and are capable of performing communications in the wider frequency band. As an example, FIG. 11 shows that the frequency band with a bandwidth of 100 MHz used in communications in downlink is comprised of five downlink component carriers (DCC1, DCC2, DCC3, DCC4, and DCC5) each with a frequency band of 20 MHz, and that the frequency band with a bandwidth of 40 MHz used in communications in uplink is comprised of two uplink component carriers (UCC1 and UCC2) each with a frequency band of 20 MHz.
Herein, in FIG. 11, downlink channels and uplink channels are respectively mapped on downlink component carriers and uplink component carriers. And the base station apparatus assigns the PDSCH to the mobile station apparatus using the PDCCH, and transmits a downlink transport block to the mobile station apparatus using the PDSCH. In other words, in FIG. 11, the base station apparatus is capable of transmitting up to five downlink transport blocks to the mobile station apparatus in the same subframe. Meanwhile, the mobile station apparatus transmits the uplink control information including the HARQ control information, the channel state information, the scheduling request and the like to the base station apparatus using the PUCCH and/or PUSCH.
Further, in LTE-A, an assignment method is proposed in case that the base station apparatus assigns the PDSCH to the mobile station apparatus using the PDCCH on a downlink component carrier (Non-patent Document 2).
FIG. 12 is a diagram to explain an example of the method of assigning the PDSCH using the PDCCH in the conventional techniques. FIG. 12 shows a part of the downlink component carriers (portion of DCC1, DCC2 and DCC3) in FIGS. 10 and 11. As shown in FIG. 12, the base station apparatus is capable of assigning a plurality of PDSCHs to the mobile station apparatus in the same subframe, using a plurality of PDCCHs on one downlink component carrier.
As an example, FIG. 12 shows that the base station apparatus assigns PDSCHs on the DCC1, the DCC2 and the DCC3, using three PDCCHs (PDCCHs respectively shown by diagonal lines, grid lines and mesh lines) on the DCC2 (the PDSCH on the DCC1 is assigned by the PDCCH shown by diagonal lines, the PDSCH on the DCC2 is assigned by the PDCCH shown by grid lines, and the PDSCH on the DCC3 is assigned by the PDCCH shown by mesh lines.) The base station apparatus is capable of transmitting up to three downlink transport blocks to the mobile station apparatus in the same subframe, using the PDSCHs respectively on the DCC1, the DCC2 and the DCC3.